Linear Systems of Equations: Effective Methods for Solving Equations

With this article you’ll learn to solve linear systems of equations. The following topics appeared 8 times in the last final exams:

Explanation

Definition

Linear systems of equations are collections of linear equations where the aim is to find the values that satisfy all the equations simultaneously. They are central to solving equations and to exam problem solving in the finals.

\begin{aligned} ax + by &= c \\ dx + ey &= f \end{aligned}

Procedure

Scheme

The addition method eliminates a variable by adding equations. This method helps you systematically solve systems of equations.

(x+y) + (x-y) = 5 + 1 \quad\Rightarrow\quad 2x = 6

Solve: x + y = 5 and x - y = 1: x = 3,\, y = 2.

In the substitution method, one variable is isolated and substituted into the other equation. This way, you can solve the system step by step.

x + 2(3 - x) = 5

Solve: y = 3 - x and x + 2y = 5: Substitute y = 3 - x in x + 2y = 5, in, simplify to -x + 6 = 5, thus x = 1,\, y = 2.

In the equalization method, you bring both equations into the form y = and set them equal.

4 + x = 2x + 2

Solve: y = 4 + x and y = 2x + 2: Substitute 4 + x = 2x + 2 equals, yielding x = 2 and thus y = 6.

Misunderstandings

Common Errors
  • It is often forgotten to pay attention to the signs, which leads to incorrect calculations in the addition method.
  • The isolation is often done incorrectly, which makes the substitution method faulty.
  • It is often overlooked to bring the equations into the same form before applying the equalization method.

Problems

1 / 3
Solve the system using the addition method:
x + y = 5, x - y = 1
2 / 3
Solve the system using the substitution method:
y = 3 - x, x + 2y = 5
3 / 3
Solve the system using the equalization method:
y = 4 + x, y = 2x + 2
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